Question to those with boosted 420a

Running a fairly built engine now for several years. I've lifted the head once before but blamed it on detonation when a fuel pump was slowly failing.

I'm back to the same issue now. I used a cometic MLS gasket and arp studs. I'm at about 18-20psi on around 14deg timing (93pump) and I'm pretty sure I'm lifting the head again. I get small amounts of compression in the cooling system. Turn the power down to 15ish psi and no more combustion pressure.

I've seen some old forum guys running close to 24ish psi before having to go to 1/2in head studs. Any other tricks to keep the head planted? I'd rather not take the block out to take to the machine shop.

I'll try to upload some pics if I can remember how lol